This is a phase II multi-center, randomized, double blind, placebo-controlled trial. The investigators are doing this study to see if a new drug, abatacept, can be used together with a calcineurin inhibitor (cyclosporine or tacrolimus) and methotrexate to provide better protection against Acute Graft versus Host Disease (aGvHD) without causing more infections. Funding Source - FDA OOPD

Chronic graft-versus-host disease (cGVHD) can be hard to diagnose, difficult to manage and contributes significantly to morbidity and mortality in hematopoietic stem cell transplantation patients. The research will look into identifying and validating cGVHD biological indicators (=bio-markers) which will be evaluated whether they can predict a future development of the disease. The study hypothesis is that a number of previously reported cGVHD bio-markers, known to be present at the time of cGVHD diagnosis, will also be present at earlier time points, before cGVHD develops. Following validation, the bio-markers will be beneficial for finding those patients who are in higher risk to develop cGVHD. By identifying the higher-risk group, which is more likely to develop cGVHD, a pre-emptive therapy might be applied in order to prevent or reduce the prevalence of the disease.